Apparatus for dewaxing oils



May 13, 1947. E. M. DONS l-:T AL A 2,420,418

` PIPARATUS FOR DEWAXNG OILS Filed Nov. 17, 1944 DEWAXED 4 OIL SOLUTIQN ATTORNEYS.

Patented May 13, 1947 'TE NT F FICE AEPARATUS FR DEWAXENG OILS Delaware Application November 17, 1944, Serial No. 563,814

(Cl. 19d-18) 2 Claims.

This invention relates to apparatus for dewaxing oils wherein selective dewaxing solvents `are employed to aid in solidifying the wax. The

lpr'oce'ss herein disclosed is claimed in a patent application iiled by us on November 13, 1944,

Serial No, 563,284, which has resulted in Patent No. 2,410,483, granted November 5, 1946. An

-ob'ject of the invention is to produce wax crystals that can be eiiiciently separated from the oil solution without retaining the usual excessive quantities of oil solution in the separated wax. Prior to this invention, the wax has been .precipitated and transmitted to a filter, or other separating apparatus, in the form of non-uniform `crystals which are not eciently separated from the oil solution. For example, in a 'filtering operation, a mixture of non-uniform wax crystals will tend to reduce the rate of filtration while .also 'trapping excessive quantities of oil solution in the wax cake on the surface of the filter.

S'For many years, this objectionable condition `has been clearly recognized and well understood `by the experts in this art, and efforts have been made to produce the desired uniform wax crystals. However, so far as we are aware, the prior efforts have failed to solve this oil problem. The conventional dewaxing processes now in general commercial use produce a rather haphazard niixture of large and small wax crystals which reduce -the :rate of iiItratiOn, while trapping excesfsi-ve quantities of oil solution in the mass of nonuni-form crystals on the iilter.

lThe system herein disclosed involves special cooperative conditions which begin by deliberate- 'ly forming a multiplicity of extremely minute wax vnuclei crystals, and continue at successive stages where we have created conditions which progressively increase the growth of the selected minute nuclei crystals. Actual tests have clearproduct containing a relatively small percentage of oil solution can be purified at a relatively low cost.

With lthe foregoing and other objects in View, the invention comprises all of the novel cooperative details herein shown and described, but

it is :to be'understood that the scope of this patent extends to modications and variations described by terms of the claims hereunto appended. The drawing is a diagrammatical view of a l2 dewaxing system embodying :features of this invention.

To illustrate one form of the invention we will ldescribe details of a blending chamber I for the `incoming `oil and solvent, and also refer to a pipe coil V2 for subsequent operations. For convenience in explaining unusual variations, the drawing specifically sets forth volumes vof 'cooled solvent to be added at lsuccessive stages, as well las speciiictemperatures at such sta-ges. However, it is to be understood that these speciiic details are .merely .for a general comprehension of an unexpected new subject, and that the invention is not limited to such details. We ldesire to begin by producing an oil solution at approximately the cloud point of the solution, or within about 10 F. of the cloud point, and this lcan be accomplished in any suitable manner.

The drawing shows that the blendinglchamber I forms a relatively large elongated passageway, and thata continuous stream of the incoming-oil charge from pipe 3 is transmitted through a heater Il and thence through pipe t5 to one end of said passageway. A continuous stream'of dewaxing solvent is transmitted from a Apipe f6 and forced through a cooler l to a pipe .8 having branches 9 leading to successive stages in Ithe elongated blending chamber I. The branches il are provided with regulating valves Ill set for gradual decreases in the admission of .cooled solvent, as suggested by specic .conditions -set forth in the drawing. Under these conditions the slowly advancing mixed stream inthe chamber I will be gradually cooled as shown at temperature indicators I i. At the beginning there is a very rapid decrease in temperature, vbut this is followed by a carefully regulated decreased cooling for the purpose of merely producing .a cloud point, or within about ten degrees of the cloud point.

We desire to carefully produce the extremely tiny wax crystals at the cloud point and thereafter uniformly increase the growth of :each Aof these nuclei wax crystals. This cloud point may be produced in any suitable manner. However, the idea of carefully producing and then very gradually enlarging the lminute wax crystals seems to be a novel subject, involving special cooperative conditions.

The `blending chamber I may beprovided lwith a rotating shaft I2 provided with agitators I 3 which cooperate with xed members M to lforoibly blend the incoming solvent with the oil. The mixture formed in this chamber .I may be discharged through a pipe IS-,to a tank 126, 4and then to a pipe I1 leading to the pipe coil 2, said pipe II having a pump I8 and valve I9, or other suitable means to regulate the delivery of the mixture to the pipe coil 2.

This pipe coil 2 is merely a diagrammatical illustration of successive passageways which may be arranged in any desired manner to provide for successive operating stages wherein the minute wax nuclei crystals are gradually enlarged for the purposes of the invention herein disclosed. However, for convenience in briey describing the invention, we have shown a single coil having an outlet 20 at the bottom leading to a chiller 2| where the mixture is subjected to comparatively rapid chilling, and then discharged through a pipe 22 to a conventional filtering apparatus including a rotary filter 23. The dewaxed solution passes through the filter and escapes through a discharge pipe 24, while the wax crystals are deposited on the periphery of said filter, so as to form a relatively thick wax cake which is removed at 25 and discharged through a conductor 26.

The coil 2 herein shown is associated with a source of dewaxing solvent which flows in a continuous stream under pressure from a pipe 2l, and through a chiller 23 to a pipe 29 having numerous branches 30 leading to successive inlets of the cooling coil 2. Each branch 3U is provided with suitable regulating means diagrammatically indicated by valves 3l. The regulating devices are carefully adjusted to progressively increase the admission of chilled dewaxing solvent to the mixture advancng through the coil 2. A specic example of increases in the admission of chilled solvent appears at the left side of the coil 2. Study of this specific example will show that relatively small but progressively increasing quantities of the chilled solvent are injected during initial stages of the growth of the tiny nuclei crystals, so as to positively provide for most gradual and uniform preliminary growth during said initial stages.

This involves one of the critical conditions in our plan for approximately uniform growth of the extremely minute nuclei crystals formed at the cloud point. However, as suggested in the specic example at the left side of coil 2, we can progressively increase the admission of chilled dewaxing solvent at subsequent stages to more rapidly increase the rate of growth of the wax crystals.

The linear velocity of the mixed stream in the coil 2 is preferably between one-fourth of a foot and three feet per second, and the pipe coil 2 is composed of pipes having progressively increasing diameters to avoid excessive increases in velocity in response to the admission of the successive solvent streams.

'I'he temperature of the mixed stream in said coil 2 is preferably reduced at a rate between two and six seconds per degree of Fahrenheit temperature. A suitable decrease in temperature is shown in a specific example at the right hand side of the coil 2, where indicators 32 are connected to successive stages in the pipe coil.

The specific illustration of temperatures, relative volumes, etc., are merely an example of one of our testing operations wherein we employed a solvent blend of 95% isopropyl acetate and 5% amyl acetate to dewax a petroleum lubricating oil stock having a pour point of 100 F., and containing about 9% wax. However, the invention is not limited to any speciiic solvent, nor to the specific example employed in describing the invention. Numerous other dewaxing solvents include methyl ethyl ketone which may be improved 'by adding toluol; acetone and benzol, isopropyl ether and butyl alcohol, methylene chloride and butyl alcohol, or any other suitable dewaxing solvent.

The drawing refers to incoming oil at a temperature of 180 F., but this merely refers to our specific example. Lower or higher temperatures may be employed. The same is true of other conditions in the illustrative example. More speciflcally stated, the incoming oil from pipe 5 is preferably at a temperature between F. and F., while the cooled solvent from pipe 8 may be at a temperature between 35 F. and 65 F. The temperature of within about 10 of the cloud point in pipes l5 and I'I may be between '75 F. and 95 F., the temperature of the solvent from pipe 29 may be 20 above or below zero; the mixture discharged at the bottom of coil 2 may be at a temperature between 30 F. and 50 F., and the resultant mixture may be quickly chilled in the chiller 2| and transmitted to the filter at any desired temperature. However, these specific temperatures are merely illustrative of desirable conditions, intended to more clearly set forth a specific arrangement of cooperative details, without limiting the scope of the patent to said temperature conditions.

In the second injection unit 2, we preferably adhere to a continuous stream line flow, at relatively low velocities, as distinguished from a turbulent now, so as to positively provide for free selective growth of the numerous individual crystals, which could not occur under highly disturbed fluid conditions. The gradual ejectionof the wax out of its normal liquid state in the solution is progressively accomplished not only by very gradual decreases in temperature, but also by the progressive anti-solvent properties of the solvent on the wax. We provide cooperative conditions in this step by step procedure which produce a `natural growth of a nearly perfect wax crystal from its minimum unit size to approximately uniform enlarged dimensions, thereby forming approximately uniform wax crystals for economical separation of the wax from the oil.

We claim:

1. In an apparatus for filtering wax from oils, an elongated blending chamber having an inlet near one end for a heated stream of wax bearing oil, and an outlet near the opposite end, said blending chamber also having a series of intermediate inlets for cooled dewaxing solvent to be mixed with and dissolved in the wax bearing oil, rotary agitators in said blending chamber, a cooling coil communicating with the outlet of said blending chamber to receive the outgoing mixture of solvent and waxy oil, said cooling coil having successive inlets for streams of cooled dewaxing solvent, and separate regulating means for the successive streams, the regulating means being set to progressively increase the rate of admission of said cooled dewaxing solvent, said cooling coil being composed of relatively small pipes having progressively increasing diameters to avoid excessive increases in velocity in response to the addition of solvent streams at said successive inlets, a chiller communicating with the relatively large discharge end of said cooling coil to continue the cooling of the waxy solution, and a filter communicating with said chiller to separate the liquid solution from the wax crystals.

2. In an apparatus for filtering wax from oils, the means vfor forming approximately uniform 5 wax crystals which comprises a cooling system provided with an elongated blending passageway having an inlet near one end for a stream of wax bearing oil, and an outlet near the opposite end, said blending passageway also having a series of intermediate inlets for cooled dewaxing solvent to be mixed with and dissolved in the wax bearing oil, cooling coils communicating with the outlet of said blending chamber to receive the outgoing mixture of solvent and waxy oil, said cooling coils having successive inlets for incoming streams of cooled dewaxing solvent, and separate regulating means for the successive streams, the regulating means being set to progressively increase the rate of admission of said cooled dewaxing solvent, said cooling coils being composed of pipes having progressively increasing diameters to avoid excessive increases in velocity in response to the addition of the progressively increasing solvent streams at said successive inlets, and a lter communicating with the relatively large end of said cooling coils to separate the liquid solution from the wax crystals.

EDDIE M. DONS. OSWALD G. MAURO.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 389,567 Hall Sept. 18, 1888 477,153 Pielsticker June 12, 1892 2,006,011 Atwell June 25, 1935 2,287,966 Brandt June 30, 1942 2,097,999 Done et al Nov. 2, 1937 

